P3: Bound invalid socket-message logging

[lovasoa]

Audit priority: P3.

Invalid socket-message logging serializes raw hostile payloads.

Refs:

• https://github.com/lovasoa/whitebophir/blob/master/server/socket/policy.mjs#L273-L299
• https://github.com/lovasoa/whitebophir/blob/master/server/observability/logging.mjs#L252-L264
• https://github.com/lovasoa/whitebophir/blob/master/server/observability/logging.mjs#L270-L280

What happens:

Rejected socket messages are logged with message: data, and non-scalar log attributes are stringified. This happens on the boundary rejection path, before the payload has a trusted shape.

Why this matters:

• Malformed input can drive avoidable allocation and log volume.
• The issue is secondary because normal message shapes have validation limits, but arbitrary invalid objects can still hit this path repeatedly.

Recommended direction:

• Log bounded metadata only: rejection reason, tool/type tags, approximate payload size, socket id, board, and client IP.
• Avoid logging the full raw message object for invalid socket payloads.
• Add a regression test for oversized/malformed invalid payloads that verifies bounded logs.